A variety of apparatus and methods are known for wrapping or pouching objects in containers, particularly objects made from flexible materials. Such known apparatus and methods are limited in their abilities to adjust readily for changes in the size of the objects, the size or format of the container, or both. Many such known apparatus and methods are also limited in their abilities to wrap or pouch objects which require more gentle handling due to their ease of damage or their unstable structure. For example, stacks of slipper sheets of x-ray film or photographic paper must be handled carefully due to the sensitivity of the film to scratches, pressure marks, and the like. In addition, stacks of sheets of such objects having slippery surface properties are easily shifted out of their desired right-rectangular stack configuration, thereby producing an irregularly shaped, skewed stack which is difficult to handle and package. Often, the objects are vacuum sealed in the pouch so that the objects will not slide from their stack configuration. The amount of vacuum affects the packaging quality, as does the heat seal required to maintain the vacuum within the sealed pouch. The vacuum and seal must be sufficient to secure the objects within the pouch, yet allow a user to tear the pouch open to access the objects.
FIG. 1 shows a pouch and an object of some typical types. Pouch 10 can be formed from a pair of preferably congruent opposed side walls 12,14 joined together by a peripheral seal 16, such as a continuous heat seal, but unjoined on one side, thereby forming an opening or mouth 18. The joined sides may include flaps, rip strips, or other features desired for a particular application. A typical object to be packaged would be a single object or an essentially right rectangular stack 20 of sheet material. The top and bottom sheet of stack 20 may be covered by dunnage cards 22,24 to protect the object during handling. Once the object has been positioned within pouch 10, pouch 10 can be evacuated of air which causes side walls 12,14 to conform generally to the shape of the object. Mouth 18 can be closed by a seal 26, to produce a packaged object of the general configuration shown in FIG. 2.
U.S. Pat. No. 5,265,397 (DePoint et al), commonly assigned, herein incorporated by reference, relates to a flexible apparatus and process for loading and sealing pouches. FIG. 3 discloses pouch 10 positioned for evacuating and sealing. A pouch evacuation apparatus 28 is provided which comprises a pneumatic actuator 30. The actuator rod of actuator 30 extends toward the rear of the apparatus and fixedly supports a transverse support block 32 for a pair of evacuator probes or tubes 34, only one of which appears in FIG. 3. Probes 34 are positioned essentially on the centerline of the open mouth of pouch 10, and are connected to a suitable vacuum source. Above and below probes 34 are mounted upper and lower pouch closing and sealing jaws 36 which comprise upper and lower pairs of pneumatic actuators 38 having actuator rods 40 which support transversely extending mounting bars 42. Attached to bars 42 are pairs of aligned, oppositely facing and transversely extending heat sealing bars or jaws 44. Actuator rods 46 of upper and lower pairs of pneumatic actuators 48 support aligned, oppositely facing and transversely extending pouch closing bars or clamping jaws 50, each having a layer 52 of foam rubber or similar resilient material on its surface facing probes 34. Actuator 30 extends probes 34 through the mouth of pouch 10 into fairly close proximity to the enclosed object. Actuators 48 are then actuated to extend clamping jaws 50 into contact with the side walls of pouch 10, thus compressing layers 52 to provide a mechanical seal between the side walls and around the extended probes 34. Vacuum is then applied to probes 34 for a time sufficient to evacuate the pouch, after which probes 34 are withdrawn behind sealing edges 44, but with the vacuum still being drawn. Actuators 38 are then actuated to press sealing jaws 44 into contact with pouch 10 to form seal 26 and complete the package. Vacuum is then stopped and actuators 38, 48 are deactuated to release the package.
While the apparatus disclosed in DePoint has achieved a level of success, the vacuum levels in the completed pouches may vary. Accordingly, there continues to be a need for an apparatus which provides precise control of the vacuum during the vacuum sealing process, provides consistent vacuum levels in the completed pouches, achieves high levels of vacuum during the vacuum sealing process. There also continues to be a need for such an apparatus which does not clog during the vacuum sealing process. Further, a need continues for a method for selectively heat sealing the pouches to provide a heat seal.